Dielectric films are an essential element in semiconductor fabrication. For example, inter-layer dielectric (ILD) films are used in integrated circuits (IC) for embedding various metal vias and metal wires of the IC. For another example, dielectric films are used in deep trench isolation features in CMOS image sensors such as FSI (front-side illuminated) image sensors and BSI (back-side illuminated) image sensors. For yet another example, dielectric films are used as lining layers in through-silicon vias (TSV) in 3D (three-dimensional) IC packaging.
One main function of the dielectric films is to electrically insulate different metal features. For example, when fabricating an IC with high-k metal gate transistors, it is a typical practice to deposit a silicon oxide film (a dielectric film) over the metal gate and form metal vias and metal wires over the silicon oxide film. The silicon oxide film is supposed to insulate the metal gate from the metal vias and metal wires. However, one issue sometimes arises: the metal gate may react with certain chemistries during the deposition of the silicon oxide film, resulting in some metal compounds mixed in the finally deposited silicon oxide film. These metal compounds may lead to circuit shorts between the metal gate and the metal vias subsequently fabricated.
Accordingly, an improved dielectric film for semiconductor fabrication and methods of making the same are desired.